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Tuesday, April 10, 2012

Meet The Leaking Transmission Corrector

If you’ve owned an old Harley for more than 20 minutes you’ve probably done this already so that means now you’ve got an opportunity here to take advantage of the situation and go do something a lot cooler than reading on the internet. For you that have owned your hog less than 20 minutes – carry on reading. Today we’re fixing a leaking transmission on a 1947 Knucklehead FL. You can get the full ‘how to’ do this in the original manual for the particular bike you have but here's a few small but more or less important tips that you won’t find in there.

Start out with getting the old worn seal out of the casing, if you don’t own the right tool to do this you can use some old screwdrivers and a pair of pliers. After you’ve done this you need to get the bearing and connecting surfaces perfectly dry - and this will take some time; first you’ll need to get the bike tilted slightly to its right side, use brake cleaner, compressed air and a paper towel, carefully so the bearing needles dosen't fall out of place, clean out the oil carefully – do not spray or blow directly at the bearing, drench a paper towel in brake cleaner and get to work, you’ll need to do this over and over because new oil will find it’s way through the bearing so it’s important to take your time until every surface is 100% dry – and stays that way, like I just said - tilt the bike over slightly to its right side.

To prevent damaging the new seal or transmission casing when pressing the seal in place you’ll most likely need to cautiously sand parts of the edge and maybe even some areas of the inner connecting surface. Be careful, you don’t want to deform the radius or get any dust inside the bearing, so do this after you’ve got the bearing and everything else all dry. I used 800 grit first and then a 2000 grit to finish it off. After that it’s back to brake cleaner, compressed air and a paper towel.

Make sure the edge is perfect, so the seal can sit by itself inside the casing (like 1 mm in or so) or it may deform or/and get scratches when pressed in. Then get it out again and coat it with Loctite 5980.

You'll need to get a new steel spacer to do this the right way; only changing the seal won’t hold the oil back for long, it’s important to clean the new seal and spacer with brake cleaner before coating. Use Loctite 5980 to coat the spacer on its connecting surfaces, and coat the high side of the seal. Spit on the inside of the seal to make sure it slides on the spacer without binding up, if you don’t have any saliva left after all the brake cleaner fumes I recommend one glass of Gin.

To press or tap in the seal you'll need to find something that's got the exact same profile as the seal, and make sure it's not a bit too small, it's very important that it's the exact same size or you’ll make the seal collapse, I used a bearing press tool that I had laying around, then I gently tapped the seal in place with a small copper hammer.

Here is the seal pressed in place, make sure you align the notch in the spacer between the threaded parts on the 4:th gear before pressing the seal in place, this is important, you do not want to turn the spacer around at all after it’s in there - and for God’s sakes do not forget to lock up the spacer with the little L-shaped key. After the first coating you’ll need to finish off all this and tighten the sprocket nut within 10 minutes or so, to make the spacer lock itself in place safely before the Loctite coating hardens. It's also important to not clean the transmission housing from old oil because a dirty motorcycle counts as credability.

I like to run the aftermarket sprocket nut with an internal seal, they won’t make any huge difference but I think they’re a little bit better than the original nut...
Like I said, if you’ve owned your hog for more than 20 minutes you’ve probably done this a few times already, however the combination of these microscopic tips, how insignificant they all may seem, are what’s kept my transmissions leak free or close enough throughout the years.